OBJECTIVES - To assess time to progression to castrate-resistant prostate cancer (CRPC) and factors influencing longer-term outcomes in patients receiving ADT in an extension to the Triptocare study (NCT01020448).

This is pertinent as the Triptocare study did not show that urinary PCA3 score was a reliable marker of cancer stage in advanced prostate cancer and was not useful for assessing response 6 months after initiation of androgen deprivation therapy (ADT) with triptorelin 22.5 mg.

MATERIALS AND METHODS - An international, multicentre, non-interventional, observational, longitudinal, prospective study involving patients from the Triptocare study. CRPC status of patients was collected for up to 3 years from ADT initiation. Patient treatment and assessments were at the investigator's discretion. Co-primary endpoints were rate of CRPC 3 years after initiating ADT and median time to CRPC. An exploratory endpoint was association of Triptocare baseline variables (including TMPRSS2-ERG score and PCA3 score) and PCA-3 score at Triptocare last value available with CRPC onset.

REULTS - Of the 325 patients in the Triptocare study safety population, 180 patients were enrolled in the Triptocare LT study (102 received continuous and 78 received intermittent ADT). CRPC rates at 3 years were 24/102 (23.5%) and 6/78 (7.7%) patients in the continuous and intermittent ADT groups, respectively. Median time to CRPC was not reached for either group. PCA3 score status at baseline was the only variable associated with a higher risk of progression to CRPC in both the intermittent and continuous ADT groups; compared with a baseline PCA3 score ≥35, PCA3 score below the level of quantification (BLQ) had a hazard ratio (HR) of 20.04 (95% CI: 2.71-148.34) and a HR=9.44 (95% CI: 2.39-37.27), respectively. Baseline metastatic disease and testosterone were additionally associated with progression to CRPC in the continuous ADT population: HR=5.20 (95%CI: 1.68-16.06) and HR=0.995 (95%CI: 0.991-0.999), respectively.

CONCLUSIONS - In men with locally-advanced or metastatic prostate cancer, a PCA3 score ≥35 at time of initiating ADT may predict a lower risk of developing CRPC in the following 3 years. This article is protected by copyright. All rights reserved.

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